Soap useful for making lubricating greases



Patented Feb. 10, 1953 SOAP USEFUL FOR MAKING LUBRICATING GREASES .lohn R. Allison and William L. Blalock, Whittier, Calif., assignors, by mesne assignments, to Lef ngwell Chemical Company, Whittier, Calif., a corporation of California Application September 23, 1949, Serial No. 117,434

15 Claims.

This invention relates to water-insoluble and oil-soluble fatty acid soaps of the type used for the manufacture of lubricating greases and as bodying agents in cil paints.

The purpose of the invention is to so modify the properties of the oil-soluble soaps of commercial stearic acids, consisting principally of saturated fatty acids having from 16 to 22 carbon atoms as materially to increase their utility for these uses.

The oil-soluble soaps to which Ythe invention applies are the salts of these acids, of which stearic acid is typical, with aluminum and with the groupII metals having atomic weights greater than 24 and less than 138.

The use of aluminum stearato and of the stearates of magnesium, calcium, zinc and barium in the manufacture of lubricating greases is well known. The stearates of strontium and cadmium have likewise been used, though to a lesser extent because of their cost.

In general terms, the soap is heated and agitated with a more or less viscous mineral oil until it dissolves (or disperses) yielding a clear `solution. On cooling under suitable conditions, the resultant mass has a buttery or gelatinous consistency, the product having a wide variety of uses in situations in which a liquid lubricant cannot be retained in place between the engaging surfaces.

The stearates of aluminum and, to a, less extent, of the other metals named, have found considerable use also as additives in small quantities to oil paints, in which they function as suspending agents for the solid pigments, tending to prevent settlement in storage,

We have discovered that the usefulness of the oil-soluble soaps of stearic and other fatty acids is materially increased by compounding with them a relatively small proportion of the salt of the same metal, or of another metal of the same group, with the 8-carbon compound 2-ethy1 hexanoic acid, also known as octoic acid. For convenience, the briefer term will be used throughout this specication, it being understood that the terms octoic acid and oc-toate, as used herein, refer to the branched chain Z-ethyl hexanoic acid and its metallic salts and not to caprylic acid H H n n H H H or its metallic salts, the latter being wholly unsuited to our purposes.

We have also discovered that the properties o the above named soaps are still further modied,

in a desirable manner, by what we term coprecipitatlon of the soaps, meaning thereby the production of a mixed oil-soluble soap by acting on an aqueous solution of a mixture of the alkalimetal soaps of the two acids with an aqueous solution of a salt of the desired metal or metals.

In producing the individual soaps to de later compounded we work inv the Wet way: for example, an aqueous solution of sodium steerate or sodium octoate is blended withan aqueous solution of an aluminum salt such as the sulfate or the chloride; the precipitate is water-washed until substantially free from soluble salts and is then iiltered, dried and pulverized.

In producing the coprecipitated soaps the sodium soaps, for example, of stearic acid and octoic acid are mixed in desired proportions in aqueous solution, or the acids themselves may be mixed and dissolved in an aqueous solution of sodium hydroxide or carbonate. The two soaps are then precipitated simultaneously by the addition of an aqueous solution of a suitable salt, such as aluminum sulfate or one of the water-soluble salts of barium, calcium, magnesium, strontium or zinc.

It is also possible, and often desirable, to 'form the soaps in situ in a grease-making oil such as a 50 viscosity red oil. In this procedure we first dissolve the two acids in the oil, which is preferably reduced in viscosity by heating. The carbonate or hydroxide of the desired metal is then added, together with a small quantity of water to promote reaction, and the mass heated with agitation and at a temperature below the boiling point of water until reaction is completed and the soaps formed. Finally, the temperature is raised and the water driven off. It is preferable to use the hydroxide of aluminum, barium, calcium or strontium or ,the carbonate of magnesium or zinc.

It is also possible, and in some cases may be desirable, to coprecipitate the soaps of the two acids with salts of more than one metal, as for example with a mixture of compatible salts, such as the chlorides or acetates, of aluminum, barium,

calcium, magnesium, strontium or zinc. This formation of the soaps with two or more metals may be produced by either of the manipulations above described.

The titer test of mixtures of the two acids is substantially a straight line function, as may be seen from the following gures:

Degrees C. 100% stearic acid 48.9 90% stearic 10% octoic 45.9 80% stearic 20%'oct'oc 42.9 70% stearic 30% octoic 39.9 stearic 40% octoic 36.8 50% stearic 50% octoic 33.6 40% stearic 60% octoic 30.0

' ate alone, the second the melting point of a blend of the stearate with aluminum octoate, and the third the ratio of stearate to octoate in the blend.

Melting Points Ratio- Stemma Saigaea-.I- stearato: Octoate ordm-degrees l degrees v The addition of aluminum octoate to aluminum stearate used in grease making has a tendency to harden the grease,`to decreasel the extent to which penetration rises when the grease is worked and, usually, to increase the extent to which hardness recovers after working. v i

' The five pairs ofy experiments Vrecorded. in the table below were made with different samples of aluminum stearate, though in each pair the same stearato was'used and the same procedure followed. An oil of 50 seconds viscosity was used in all the tests. The first column in the table shows the total quantity of soap used in the test; the second the ratio of stearate to octoate in the soap; the third the initial penetration `of the grease, after cooling; the fourth thev penetration after Working, and the fththe penetration after healing for 24 hours following working.

The comparisons of the above table are'shown graphically in Figs. l to 5 inclusive of the attached drawings, in' which the left'hand point is located by the initial penetration, the medial by the penetrationafter working, and the right hand by the penetration after healing. In each of these iigures the -fsolid line shows the behavior of the grease compounded with ystraight stearate, the broken line representing the 'grease containing octoate. Y

The following are yexamples of coprecipitated soaps of certain metals other than aluminum, the soaps of the remaining metals namedA above being,r

formed in the same general manner.

Zinc soap 80 grams stearic acid and 3.2 grams octoic acid were dissolved in an aqueous solution o1"13l grams sodium hydroxide. The oilsoluble soaps were precipitated from this solution 'byintermixture with an aqueous solution of Ae526 glfamS Qlysial* line zinc sulfate, Zn( S04) .61120. The curcly precipitatewas washed free from sodium sulfate, l-

tered and dried. The yield is theoretical.

Magnesium-aluminum soup sulfate, AMSOQ?. and 80 grams magnesium sulwhich renders the grease rm without excessive fate, Mg(SO4) .'ZHzO Were simultaneously dissolved in water and the soaps were precipitated by mixing the two solutions. This is an example of a. soap of two acids with two metals.

Barium soap gramspstearic acid and 9.3 grams octoic acid were saponiiied with lgrams sodium hydroxide in aqueous solution and precipitated with an aqueous solution of e16.3 grams barium chloride.

strontium soap 40` grams stearic. acid and 4.6 grams octoic acid were dissolved in 700 grams 50 viscosity red oil at 160.,F. 10 grams water and 29.3 grams strontium hydroxide, Sr(OH)z.8l-I2O were then added with vigorous stirring and the temperature raised, as fast Las frothing would permit, to about 260 F. at y,which point it was held until frothing ceased and a clear solution of the strontium soap in oil was produced. This solution was viscous while hot and set to a firm grease on cooling.

Theses'oaps are highly similar physically and may bersubstituteci for each other in desired proportions in the grease formula. The eiiects Y producedvary slightly as one metal is substituted J or otheroil-soluble soap used in grease making includethe following:

(a) The temperature at which the grease in verts, with separation of the soap from the oil, is materially raised, lessening the risk of destruction of the lubricating nlm by overheating of .a-

bearing;

- (b) The wearing property of the greaseis improved-possibly by reason of its better retentionin the-bearing;

(c) 'A smooth, buttery consistencyis developed hardness; i

' (d). The productionV of a clear grease having-an attractive appearance [is` much facilitated and,

` ordinarily, the .working ,temperature is somewhat lowered, with thev result thatv the colorof greasefis improved; A v

.The grease is rendered considerably more' adherent tothe surfaces to be lubricated:

(f) "A degree ofcohesiveness is developedwhicl'i," so `far as we are aware, 'cannotevenfbe 'ap proached in any other manner. This striking4 andv surprising effect may be carried to any'de-- sired'extent, as is illustrated by the results of the4 following experiment.

Three batches of grease were prepared by the incorporation of 7% of soap in a mineral oil, the sameroil and the `same procedure being used ineach. The soap used in the 'iirst batch was aluminum stearate; that Aused in the second batch was a blendof the same stearate with aluminum octoate in theratio stearate:5 octoate; that used in the third batchwas a blender" the samestearate with the same octoate in theratio 79 steamer@ octoate.. y

the

The product of the'flrstbatch, vrhenpogld, had a soft consistency, lust short v of ovnng when the container was inverted, and had orly slight cohesiveness, the string formed on dipping a rod into the mass and withdrawing it being but a small fraction of an inch in length. The second batch was rmer and somewhat elastic and could be pulled into strings two or three inches long. The third batch, containing a large proportion of the octoate, was highly elastic, resembling raw rubber in this respect, and could be pulled into s rings a foot or more in length which, on breaking, snapped vback into the mass from which they were drawn.

This property of stringiness, which was iurther developed in the third batch than it would be in a commercial grease, is highiy valuable. Greases having this property may be made soft enough to be be readily injected into close bearings While at the same time they are highly adhesive to metal surfaces and are sftrongltr retained in relatively loose bearings euch as spring shackles.

Another surprising .and very useful property Qi the .octoates is that of increasing the viscosity of oil solutions cf .the stearates. This pro,cty is difficult to measure in the viscous oils and in the concentrations used in grease but may readily be measured in solution in an aromatic solvent such as xylene.

The figures in the following table show `the viscosity, in centipoises, ci 2 percent xylcne soli;n tions of two blends of aluminum stearato with aluminum octoate, one of these being a mechanical mixture and the other coprecipitated, and of one blend of aluminum stearato with aluminum caprylate, this blend being coprecipitated.

These figures, which are shown graphically in Fig. 6 of the attached drawings, show how the viscosity of the solution increases with the addition of increasing proportions of the octoate, While it decreases when the caprylic acid soap is substituted for the octoate. They also illustrate the more rapid rise of viscosity when the two soaps are simultaneously precipitated.

The relation of octoate to stearato in the coinpound soap may vary over a wide range, dependint.r on the use to which the soap is to be put and the characteristics desired in the product in which it is to be used. Thus, in the manufacture of a lubricating grease, the proportion of soap in the grease may be from 4% to 10% of the total Weight and Will ordinarily be from 5% to 7%, while the proportion of octoate in the soap itself may be as small as 1% and as large as 35% of the Weight of soap, With the ordinarily preferred range from about 2% to about 10%.

For use as an additive to oil paints, the total soap in the paint must be restricted to prevent livering of the paint yand Will be within the range from 1/2% to about 3% of the total Weight. On the other hand, the proportion of octoate in the soap used for this purpose may be greater, as for example from 1% to 50% of the weight of the soap, with `the o rdmarly preferred range from fabout to about :30% .of the soap weight.

'We claim as our invention:

l. A compound soap adapted to the manufacture of 'lubricating greases and as an additive to oil paints, consisting of a stearato of a metal yselected from the Ygroup consisting of aluminum, barium, calcium, magnesium. strontium and zinc together with a .soap oi 2-ethyl hexanoic acid with ,a metal selected from the same group, llast said soap representing from 1% -to 50% of the weight of said ,compound soap.

2. `A .compound soap as described in claim 1, in which the soap of Z-.ethyl hexanoic acid represents from 2% to 10% .of the total dry weight.

3. AV compound soap adapted to thamanufac- Y ture of lubricating greases and as an additive to oil paints, ,consisting of aluminum stearato together with a soap of 2-.ethyl hexanoic acid with a metal selected from the group consisting of aluminum, barium, calcium, magnesium, strontium and zinc, last said soap representing from 1% to 50% of .the Weightof said compound soap.

4. A compound soap as described in claim 3, in which `thesoap of 2-ethyl hexanoic acid represents from 2% to 10% of the total dry weight.

V5. A .compound soap adapted to the manufacture of lubricating greases and as an additive to oil paints, consisting .of aluminum stearato together with an aluminum soap of 2ethyl hex- Ianoic acid, last said soap representing from 1% to `50% o f the Weight of said compound soap.

6. A compound soap as .described in claim 5, in which the soap of 2-ethyl hexanoic acid represents from 2% to 10% of the total dry weight.

7. A compound soap adapted to the manufacture of lubricating greases and 'as an additive to oil paints, consisting of a stearato of a metal selected from the group consisting of aluminum, barium, calcium, magnesium, strontium and zinc, together with a soap of 2-ethyl hexanoic acid with a metal selected from the same group, last said soap representing from 1% to 50% of the weight of said compound soap, said compound soap being in the condition produced by simultaneous precipitation of the two component soaps from an 'aqueous solution of the corresponding alkali-metal soaps and having a higher viscosity in 2% xylene solution than a mixture in like proportions of the separately precipitated soaps.

8. A compound soap as described in claim 7, in which the soap of 2-ethyl hexanoic acid represents from 2% to 10% of the total dry Weight.

9. A compound soap adapted to the manufacture of lubricating greases and as an additive to oil paints, consisting of aluminum stearate together with a soap of 2ethyl hexanoic acid with a metal selected from the group consisting of aluminum, barium, calcium, magnesium, strontium and zinc, last said soap representing from 1% to 50% of the weight of said compound soap, said compound soap being in the condition produced by simultaneous precipitation of the two component soaps from an aqueous solution of the corresponding alkali-metal soaps and having a higher viscosity in 2% xylene solution than a mixture in like proportions of the separately precipitated soaps.

10. A compound soap adapted to the manufacture of lubricating greases and as an additive to oil paints, consisting of aluminum stearato together with an aluminum soap of 2ethyl hexlanoic acid, last said soap representing from 1% to 50% of the Weight of said compound soap, said compound soap being in the condition pro- Aduced by the simultaneous precipitation of the twocomponent soaps from'a'n"aquedussolutionbf the corresponding' alkali-metal soaps and having a. higher viscosity in 2% xylerie solution' than a mixture in like proportions ofthe 'separately precipitated soaps. Q',

11. The method of producing a compoundjsoap of. st'earic acid and Z-ethyl'hexanoic acid which consists in bringing alk'ali-metalsoaps of said acids into joint aqueous solution, and coprecipitating water-insoluble soaps .of said Vacids by mixing with said solution 4an aqueous-solution of a water-soluble salt of a metal selected from the group consisting -of aluminum, barium, calcium, magnesium, strontium and zinc.

12. The method-of 'producing a compound soap yof stearic lacid andZ-ethyl hexanoic acid which consists in bringing alkali-metal soaps of lsaid acids into joint aqueous solution, and coprecipitating the aluminum soaps of said acids by mixing with said solution an aqueous solution of a water-soluble salt of aluminum;

13. The method ofproducing a compoundzjsoap of stearic acid Aand 2-ethyl h exanoic acid which consists in bringing alkali-metal soapsof said acids vinto joint aqueous solution, and coprecipif tating water-insoluble soaps of said acids by mixing with said solution a'n aqueous solution containing compatible water-soluble salts of at least two metals selected from the group consisting of `Aaluminum, barium, strontium and-zinc.

14.1The method of producinga compound soap of stearic acid anol-y 2-ethy1 hexanoic-acid which calcium, magnesium,

8 consists in bringing alkali-metall soaps of said acids 'into' joint aqueous solution, and coprecipitatng the barium salts of said acids by mixing with said solution an aqueous solutionof a water- 5 soluble salt of barium.

'15. The method of producing a compound soap of stearic acid and Z-ethyl hexanoic acid which consists in bringing alkali-metal soaps of said acids into joint aqueous solution, and coprecipi- 10 tating the calcium soaps of said acids by mixing with said solution an aqueous solution of a watersoluble compound of calcium.

JOHN R. ALLISON.v 15 WILLIAM L. BLALOCK.

REFERENCES CITED The following references are of record in the le of this patent:

20 UNITED STATES PATENTS Number Name Date 1,976,182 Meidert Oct. 9, 1934 2,338,128 Minich Jan. 4, 1944 2,350,688 Licata June 6, 1944 :.25 2,417,071 Gebhart et al Mar. 11, 1947 2,447,064 Gebhart et al Aug. 17, 1948 2,448,721 Licata Sept. 7, 1948 2,456,824 Fischer Dec. 21, 1948 0 OTHER REFERENCES Allens Commercial Organic Analysis, vol.v II, Copyright 1910, 4th ed., Pub. by P. Blakistons Son and Co., Philadelphia. Pa., pgs. 187, 188 and 330. 

1. A COMPOUND SOAP ADAPTED TO THE MANUFACTURE OF LUBRICATING GREASES AND AS AN ADDITIVE TO OIL PAINTS, CONSISTING OF A STEARATE OF A METAL SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, BARIUM, CALCIUM, MAGNESIUM, STRONTIUM AND ZINC TOGETHER WITH A SOAP OF 2-ETHYL HEXANOIC ACID WITH A METAL SELECTED FROM THE SAME GROUP, LAST SAID SOAP REPRESENTING FROM 1% TO 50% OF THE WEIGHT OF SAID COMPOUND SOAP. 